As a conventional auto-steerable power steering device, the device disclosed in Patent Document-1 is known.
That is, the known power steering device is of a rack-and-pinion type hydraulic power steering device and generally comprises an input shaft connected to a steering wheel, an output shaft relatively rotatably connected to the input shaft through a torsion bar, a rotary valve arranged between the input and output shafts around a lower end portion of the input shaft and a hollow motor arranged around an upper end portion of the input shaft. An optimal steering assist control is carried out based on a detection result by a torque sensor including a first resolver disposed on an outer surface of the input shaft and a second resolver disposed on an outer surface of the output shaft and output signals produced by a vehicle speed sensor, etc.